Citigroup announced that one percent of its credit card accounts have been accessed by hackers. The news, they say, was brought to their attention by “routine monitoring.” Citigroup has 21 million account holders, which means that 1% is as many as 210,000 accounts.

According to Financial Times, names, account numbers, and addresses were viewed. However, Citi says that Social Security numbers, birth dates, card expiration dates and security codes were not compromised. In a statement printed by Financial Times, Citigroup says, “a computer breach may have given hackers access to the data of hundreds of thousands of bank card customers.” They add that the hacking was discovered “in early May.”

So…why is it just being reported NOW?

This breach comes on the heels of other high-profile hacker attacks, including ones against multiple Sony Corp. sites. An attack against Sony’s Playstation Network site affected more than 100 million online accounts and “forced the site to temporarily shut down.

Unfortunately, these types of reports are becoming more and more common. Making sure that your passwords are extremely hard to crack (i.e. not making your password “password”) is one way to help prevent hacking. If you think your account(s) have been hacked, contact your credit card company immediately.